The present invention relates to a measuring apparatus for pulley of a continuous variable transmission, and particularly relates to the measuring apparatus for the pulley that is capable of measuring configurations and positional accuracies of the pulley.
Generally, the pulley is a principal component of the continuous variable transmission. A movable pulley is fitted to a fixed pulley via a ball spline so as to rotate in opposite direction with respect to each other, and a pulley width between a conical surface of the fixed pulley and a conical surface of the movable pulley varies by the axial relative movement of the movable pulley.
In such a variable width pulley, it is required to evaluate the configuration/positional accuracies of a ball groove of a ball spline and a conical surface of the pulley in order to control the qualities. Therefore, conventionally the configurations are measured by providing detecting members that employ reference balls the number of which are the same as the grooves. Each of the reference balls has a specified diameter. The reference balls are pressed with a pressure via a spring into a groove portion on a workpiece, and then amounts of displacements are measured. That is, at this time, a circumferential displacement and a radial displacement are compared with a master. Alternatively, in the other conventional technology the configurations are measured with a copying/tracing measurement that utilizes a three-dimensional measuring apparatus.
In a Japanese Utility Model Laid-Open No. 56708/1994, disclosed is a technology for measuring an irregular relative movement (amount of angular displacement) between both of the workpieces when one of the workpieces is fixed and the other workpiece is rotated about the axis of the rotation by an actuator just as a male pulley and a female pulley are assembled.
However, with the measuring technology in which the detecting member using the reference ball of a specified diameter is pressurized into the groove, the configuration measurement of the ball groove, a tapered angle of the conical surface, and other geometric positional accuracy cannot be evaluated quantitatively. In addition to this, since the number of samplings is limited/reduced due to the fact that the number of the detecting member is limited, the repeatability is inappropriate. Further, the pressurizing force of the spring easily varies, thereby disadvantageously lowering a measuring accuracy and deteriorating a zero point setting accuracy at the time of master setting.
In the copying/tracing measurement by the three-dimensional measuring apparatus, the sampling point is rough (for example, 10 points/4 mm approx.), and thus it is difficult to measure with high accuracy because of variations in repeatability. Likewise, in the technology in which the irregular (backlash) movement of the pulley assembly in the assembled state is measured disclosed in the Japanese Utility Model Laid-Open No. 56708/1994, lack of information on the configuration or positional accuracy of the other parts other than the ball groove makes the accurate control difficult. In addition to this, in the case of assemblies having significant irregular movements, it may be necessary to follow up the cause by disassembling it again, which is troublesome and is not necessarily advantageous to the productivity and to the quality control.
An object of the present invention is to provide a measuring apparatus for continuous variable transmission pulleys that can measure a configuration and a positional accuracy of a continuous variable transmission pulley quantitatively and can contribute to an improvement of a quality of finished products and lowering costs.
In order to achieve the above described object, a measuring apparatus for a pulley having a ball groove for a ball spline and a conical surface for varying a pulley width of the pulley, the measuring apparatus according to a first aspect of the present invention comprising:
a workpiece holding post for rotatably holding the pulley about an axis of the pulley;
a slide table slidable in a radial direction of the measuring apparatus;
a measuring post slidably mounted on the table in a tangent direction orthogonal to the radial direction of the measuring apparatus;
a detecting head slidably mounted on the measuring post in an axial direction orthogonal to both of the radial and tangent directions of the measuring apparatus, the detecting head having a probe including a ball of a specified diameter formed at the tip thereof; and
a processor for controlling movements of the slide table, the measuring post and the detecting head to allow the probe to be brought into contact with a portion of the pulley to-be-measured, and for measuring configurations and positional accuracy thereof based on displacement data detected by the detecting head.
In the measuring apparatus, it is preferable that the processor measures, at least one of:
(a) a groove diameter of the ball groove;
(b) an angle of intersection defined by intersecting a line connecting the center of an ideal circle and one of the two contact points and a line connecting the center of the ideal circle and the center of a measuring reference of the pulley when an ideal circle of a specified diameter is brought into contact with the ball groove at two contact points,
(c) a divided angle defined by intersecting lines connecting the center of a measuring reference of the pulley and each of the centers of a plurality of ideal circles, wherein each of the ideal circles has a specified diameter and is brought into contact with the respective ball groove at two contact points,
(d) a diameter of an outer circle of an ideal circle is, wherein the ideal circle has a specified diameter and is brought into contact with the respective ball groove at two contact points,
(e) a deviation between the center of a measuring reference of the pulley and the center of an outer circle to which a plurality of ideal circles are inscribed, wherein each of the ideal circles has a specified diameter and is brought into contact with the respective ball groove at two contact points,
(f) a diameter of an inner circle to which a plurality of ideal circles are circumscribed, wherein each of the ideal circles has a specified diameter and is brought into contact with the respective ball groove at two contact points,
(g) a deviation between the center of a measuring reference of the pulley and the center of an inner circle to which a plurality of said ideal circle are circumscribed, wherein the ideal circle has a specified diameter and is brought into contact with the respective ball groove at two contact points,
(h) circumferential and radial deviations in a lead of the ball groove,
(i) a tapered angle of the conical surface;
(j) a deviation in a normal direction with respect to a specified angle line of the conical surface, and
(k) a dimensional deviation with respect to a measuring reference of the conical surface.
In the above-mentioned measuring apparatus, it is preferable that the processor controls the slide table and the measuring post simultaneously to move the probe in the radial and tangential directions in the state of being in contact with the ball groove to carry out a copying measurement at many points, carries out circular-approximation by processing data on displacement in the radial direction and data on displacement in the tangential direction detected by the detecting head during the copying measurement at many points, and obtains an approximated diameter of the circle obtained by the circular-approximation as the groove diameter of the ball groove.
Further, in the measuring apparatus, it is preferable that the processor determines a measuring reference circle to which the tip of the prove should move based on several sampling data obtained prior to a copying measurement at many points, and controls the slide table and the measuring post simultaneously.
In the above-mentioned measuring apparatus, it is also preferable that the processor processes displacement data obtained by a copying measurement at many points, obtains a position of the center of the ideal circle assuming that the center of the circle obtained by approximating the ball groove, the contacting point, and the center of the ideal circle are on the same line, and obtains the angle of the intersection based on the position of the center of the ideal circle.
Further, in the measuring apparatus, it is preferable that the processor measures the divided angle based on the respective center positions of the ball at the moment when the probe with a ball diameter corresponding to the ideal circle is brought into contact with a plurality of ball grooves.
Moreover, in the above-mentioned measuring apparatus, it is preferable that the processor obtains the diameter of the circle passing through the respective center positions of the ball when the probe with a ball diameter corresponding to the ideal circle is brought into contact with the plurality of ball grooves, and adds or subtracts the ball diameter of the probe to or from the obtained diameter of the circle to determine the diameter of the circle in which a plurality of ideal circles are inscribed or the diameter of the circle to which a plurality of ideal circles are circumscribed.
In addition, in the measuring apparatus, it is preferable that the processor determines a line containing the apex of the conical surface obtained by controlling the measuring post to move in the tangent direction with the probe kept in contact with the conical surface of the pulley as a measuring reference centerline, carries out a copying measurement at many points by controlling the slide table and the measuring post simultaneously while moving the probe along the measuring reference centerline, and obtains the tapered angle of the conical surface based on data on displacement in the radial direction and data on displacement in the axial direction detected by the detecting head during the copying measurement at many points.
Note that in the above-measuring apparatus, the line acting as the measuring reference centerline is directed to a line which contains the apex of the conical surface and extends perpendicular to the tangential direction.
In other words, according to the above-mentioned measuring apparatus, the tip of the probe of the detecting head mounted on the measuring post on the slide table is brought into contact with the portion-to-be-measured of the pulley held on the workpiece holding post, and the configuration and the positional accuracy of the portion-to-be-measured are measured by measuring the absolute space coordinate based on displacement data detected by the detecting head.
At least one of (a) the groove diameter of the ball groove on the pulley, (b) an angle of the intersection defined, when an ideal circle of a specified diameter is brought into contact with the ball groove at two points, by intersecting a line connecting the center of the ideal circle and the contact points and the line connecting the center of the ideal circle and the center of the measuring reference, (c) an angle divided by a group of lines connecting each of the centers of the plurality of the ideal circles and the center of the measuring reference, (d) a diameter of the outer circle to which a plurality of the ideal circles are inscribed, (e) a deviation between the center of the outer circle and the center of the measuring reference, (f) the diameter of the inner circle to which a plurality of the ideal circles are circumscribed, (g) the deviation between the center of the inner circle and the center of the measuring reference, (h) circumferential and radial deviations in the lead of the ball groove, (i) a tapered angle of the conical surface of the pulley, (j) the deviation in the normal direction with respect to the specified angle lines of the conical surface, and (k) a dimensional deviation with respect to the measuring reference of the conical surface is measured.
The slide table and the measuring post are controlled simultaneously to move the probe in the state of being in contact with the ball groove to carry out the copying measurement at many points in the direction of the radial axis, or in the direction of the movement of the slide table, and in the direction of the tangent axis, or the direction of the movement of the measuring post on the slide table. Then data on displacements in the direction of the radial axis and the data on the displacement in the direction of the tangent axis detected by the detecting head during the copying process at many points are processed and estimated by a circular approximation, and the diameter of approximated circle is obtained as a groove diameter of the ball groove.
The measuring reference circle on which the tip of the probe should move along is determined based on the sampling data obtained at several points prior to the copying measurement of the ball groove, and the slide table and the measuring post are controlled simultaneously to carry out the copying measurement along the measuring reference circle.
Displacement data at many points obtained by the copying measurement of the ball groove is processed to assume that the center position of the circle obtained by approximating the ball groove, the contacting point, and the center position of the ideal circle are on the same line, and the angle of intersection is obtained based on the center position.
The angle is measured based on the respective center positions of the ball at the moment when the probe with a ball diameter corresponding to the ideal circle is brought into contact with a plurality of the ball grooves.
The diameter of the circle passing through the respective center positions of the ball when the probe with the ball diameter corresponding to the ideal circle is brought into contact with the plurality of the ball grooves is obtained, and the ball diameter of the probe is added to or subtracted from the diameter of the circle to determine the diameter of the outer circle in which the plurality of the ideal circles are inscribed or the diameter of the inner circle to which the plurality of the ideal circles are circumscribed.
The apex of the conical surface obtained by controlling the measuring post to move in the direction of the tangent axis with the probe kept in contact with the conical surface of the pulley is determined as the measuring reference centerline, and the copying measurement at the many points is carried out by controlling the slide table and the measuring post simultaneously while moving the prove along the measuring reference centerline in the direction of the radial axis. Then the tapered angle of the conical surface is obtained based on the data on the displacements in the direction of the radial axis and the data on the displacement in the direction of the axial axis detected by the detecting head during the copying measurement at many point.